Research is continued on DNA replication in Eukaryotes and Prokaryotes. Both genetic and physiological experiments are outlined. Eukaryotic studies will concentrate on DNA replication in cultures of plant cells. Using a newly developed soybean cell suspension culture system, intermediates of replication will be isolated and analyzed and structural differences of the chromosome related to the regulation of replication. Bacterial studies will continue a genetic analysis of the regulation of replication. Two types of genetic suppression will be used extensively: external (second site) suppressors will be sought for genetic functions isolated and described during the previous grant period; using ts suppressor t-RNA, amber mutations will be sought in essential DNA replication genes. These will be used to further analyze the regulation of replication.